<s>
The	O
.NET	B-Operating_System
Persistence	I-Operating_System
API	I-Operating_System
,	O
also	O
referred	O
to	O
as	O
NPA	O
,	O
is	O
a	O
persistence	O
and	O
object-relational	B-General_Concept
mapping	I-General_Concept
(	O
ORM	O
)	O
specification	O
for	O
the	O
.NET	B-Application
framework	I-Application
.	O
</s>
<s>
NPA	O
is	O
based	O
on	O
the	O
Java	B-Language
Persistence	I-Language
API	I-Language
(	O
JPA	O
)	O
,	O
which	O
is	O
the	O
standard	O
persistence	O
API	O
in	O
the	O
Java	B-Language
world	O
.	O
</s>
<s>
The	O
main	O
purposes	O
of	O
the	O
.NET	B-Operating_System
Persistence	I-Operating_System
API	I-Operating_System
(	O
NPA	O
)	O
are	O
:	O
</s>
<s>
To	O
provide	O
a	O
vendor-free	O
persistence	O
API	O
for	O
.NET	B-Application
,	O
making	O
switching	O
from	O
one	O
persistence	O
provider	O
to	O
another	O
easier	O
(	O
avoiding	O
vendor	O
lock-in	O
)	O
.	O
</s>
<s>
To	O
provide	O
a	O
cross-language	O
persistence	O
API	O
by	O
extending	O
the	O
popular	O
Java	B-Language
Persistence	I-Language
API	I-Language
(	O
JPA	O
)	O
to	O
all	O
the	O
.NET	B-Application
programming	O
languages	O
.	O
</s>
<s>
Support	O
of	O
persisting	O
POCO	B-Language
(	O
plain	B-Language
old	I-Language
CLR	I-Language
objects	I-Language
)	O
objects	O
(	O
entities	O
)	O
.	O
</s>
<s>
Using	O
external	O
XML	B-Protocol
-	O
meta	O
data	O
is	O
specified	O
in	O
external	O
XML	B-Protocol
resource	O
files	O
.	O
</s>
<s>
First	O
implementation	O
,	O
NPA	O
for	O
NHibernate	B-Language
,	O
was	O
released	O
in	O
December	O
2011	O
.	O
</s>
